High performance process oil based on distilled aromatic extracts

ABSTRACT

Naphthenic process oils are made by blending one or more naphthenic vacuum gas oils in one or more viscosity ranges with a high CA content distilled aromatic extract feedstock to provide at least one blended oil, and hydrotreating the at least one blended oil to provide an enhanced CA content naphthenic process oil. The order of the vacuum distillation and blending steps may be reversed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/572,740filed Nov. 8, 2017 (scheduled to issue on Jan. 31, 2023 as U.S. Pat. No.11,566,187 B2), which is a national stage filing under 35 U.S.C. § 371of International Application No. PCT/US2016/031857 filed May 11, 2016,which claims priority under 35 U.S.C. § 119 to U.S. ProvisionalApplication No. 62/160,089 filed May 12, 2015, the disclosures of whichare incorporated herein by reference.

TECHNICAL FIELD

This invention relates to rubber process oils and their use.

BACKGROUND

Process oils are obtained in the refining of petroleum, and are used asplasticizers or extender oils in the manufacture of tires and otherrubber products. Process oils may be classified based on their aromaticcarbon content (C_(A)), naphthenic carbon content (C_(N)) and paraffiniccarbon content (C_(P)), as measured for example according to ASTM D2140.Distillate Aromatic Extract (DAE) process oils contain considerable(e.g., about 35 to 50%) C_(A) content, and have been used as processoils for truck tire tread compounds and other demanding rubberapplications. However DAEs also contain benzo[a]pyrene and otherpolycyclic aromatic hydrocarbons (PAH compounds, also known aspolycyclic aromatics or PCA) that may be classified as carcinogenic,mutagenic or toxic to reproduction. For example, European CouncilDirective 69/2005/EEC issued Nov. 16, 2005 prohibited the use after Jan.1, 2010 of plasticizers with high PAH content.

High viscosity naphthenic oils have been used as DAE process oilsubstitutes. However, due to the generally lower C_(A) content ofnaphthenic oils compared to that of DAEs, some rubber compoundreformulation may be required to recover or maintain acceptableperformance. Also, a variety of test criteria may need to be satisfiedfollowing reformulation. For tires, the test criteria may include wetgrip (tan delta at 0° C.), rolling resistance (tan delta at 60° C.),skid resistance, dry traction, abrasion resistance and processability.This long list of potential test criteria has made it difficult to findsuitable replacements for DAE process oils.

Accordingly, there remains an ongoing need for materials that canreplace DAE process oils and thereby reduce or minimize PAH content,without unduly compromising the performance of rubber formulationsemploying such replacement materials compared to formulations employinga DAE process oil.

SUMMARY

The present invention provides, in one aspect, a method for makingnaphthenic process oils, the method comprising:

-   -   a) vacuum distilling residual bottoms from a naphthenic crude        atmospheric distillation unit to provide one or more vacuum gas        oils in one or more viscosity ranges;    -   b) blending at least one such vacuum gas oil with a high C_(A)        distilled aromatic extract feedstock to provide at least one        blended oil; and    -   c) hydrotreating the at least one blended oil to provide an        enhanced C_(A) content naphthenic process oil;        wherein the feedstock and naphthenic process oil each have        greater C_(A) content than that of a comparison oil made by        similarly hydrotreating the at least one such vacuum gas oil        alone.

The present invention provides, in another aspect, a method for makingnaphthenic process oils, the method comprising:

-   -   a) atmospheric distilling naphthenic crude to provide one or        more atmospheric gas oils in one or more viscosity ranges and        residual bottoms;    -   b) vacuum distilling the residual bottoms to provide one or more        vacuum gas oils in one or more additional viscosity ranges;    -   c) blending at least one such vacuum gas oil with a high C_(A)        distilled aromatic extract feedstock to provide at least one        blended oil; and    -   d) hydrotreating the at least one blended oil to provide an        enhanced C_(A) content naphthenic process oil having greater        C_(A) content than that of the at least one such vacuum gas oil;        wherein the feedstock and naphthenic process oil each have        greater C_(A) content than that of a comparison oil made by        similarly hydrotreating the at least one such vacuum gas oil        alone.

In another embodiment the present invention provides a method for makingnaphthenic process oils, the method comprising:

-   -   a) blending residual bottoms from a naphthenic crude atmospheric        distillation unit with a high C_(A) distilled aromatic extract        feedstock to provide a blended oil;    -   b) vacuum distilling the blended oil to provide one or more        vacuum gas oils in one or more viscosity ranges; and    -   c) hydrotreating at least one of the vacuum gas oils to provide        an enhanced C_(A) content naphthenic process oil;        wherein the feedstock and naphthenic process oil each have        greater C_(A) content than that of a comparison oil made by        similarly vacuum distilling and hydrotreating the residual        bottoms alone.

In a further embodiment the present invention provides a method formaking naphthenic process oils, the method comprising:

-   -   a) blending naphthenic crude with a high C_(A) distilled        aromatic extract feedstock to provide a blended oil;    -   b) atmospheric distilling the blended oil to provide one or more        atmospheric gas oils in one or more viscosity ranges and        residual bottoms;    -   c) vacuum distilling the residual bottoms to provide one or more        vacuum gas oils in one or more additional viscosity ranges; and    -   d) hydrotreating at least one of the vacuum gas oils to provide        an enhanced C_(A) content naphthenic process oil;        wherein the feedstock and naphthenic process oil each have        greater C_(A) content than that of a comparison oil made by        similarly atmospheric distilling, vacuum distilling and        hydrotreating the naphthenic crude alone.

The present invention provides, in yet another aspect, a method formaking naphthenic process oils, the method comprising:

-   -   a) blending a naphthenic vacuum gas oil having a viscosity of at        least 60 SUS at 38° C. (100° F.) with a high C_(A) distilled        aromatic extract feedstock to provide a blended oil; and    -   b) hydrotreating the blended oil to provide an enhanced C_(A)        content naphthenic process oil;        wherein the feedstock and naphthenic process oil each have        greater C_(A) content than that of a comparison oil made by        similarly hydrotreating the naphthenic vacuum gas oil alone.

The present invention also provides a naphthenic process oil comprisinga hydrotreated blend of a) at least one naphthenic vacuum gas oil havinga viscosity of at least 60 SUS at 38° C. (100° F.) and b) a high C_(A)distilled aromatic extract feedstock having greater C_(A) content thanthat of a comparison oil made by similarly hydrotreating the at leastone naphthenic vacuum gas oil alone.

DAEs for use in the above method may be obtained from a solventextraction unit that extracts an aromatic fraction from a crudedistillate, typically a paraffinic crude distillate. The enhanced C_(A)content naphthenic process oils obtained from the above methods haveincreased aromatic content and improved solvency in rubber compoundscompared to conventional naphthenic process oils, and may be used toreplace conventional DAE process oils.

A DAE may be hydrotreated by itself to produce an improved process oil,but doing so on a commercial scale can be difficult due to the largeexotherm that may occur during the hydrotreating reaction. Use of thedisclosed blended oil enables the naphthenic vacuum gas oil to serve asa heat sink that moderates the heat of the DAE hydrotreating reaction,thereby facilitating improved hydrotreating reaction control withreduced likelihood that an uncontrollable exotherm might occur. Theblended oil can be prepared using relatively low DAE amounts.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 through FIG. 5 are schematic diagrams illustrating the disclosedmethod.

Like reference symbols in the various figures of the drawing indicatelike elements.

DETAILED DESCRIPTION

Numerical ranges expressed using endpoints include all numbers subsumedwithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4 and5). All percentages are weight percentages unless otherwise stated.

The term “8-markers” when used with respect to a feedstock, processstream or product refers to the total quantity of the polycyclicaromatic hydrocarbons benzo(a)pyrene (BaP, CAS No. 50-32-8),benzo(e)pyrene (BeP, CAS No. 192-97-2), benzo(a)anthracene (BaA, CAS No.56-55-3), chrysene (CHR, CAS No. 218-01-9), benzo(b)fluoranthene (BbFA,CAS No. 205-99-2), benzo(j)fluoranthene (BjFA, CAS No. 205-82-3),benzo(k)fluoranthene (BkFA, CAS No. 207-08-9) and dibenzo(a,h)anthracene(DBAhA, CAS No. 53-70-3) in such feedstock, process stream or product.Limits for these aromatics are set forth in European Union Directive2005/69/EC of the European Parliament and of the Council of 16 Nov.2005, at 10 ppm for the sum of the 8-markers, and 1 ppm forbenzo[a]pyrene. PAH 8-marker levels may also be evaluated using gaschromatography/mass spectrometry (GC/MS) procedures to provide resultsthat will be similar to those obtained using European standard EN16143:2013.

The term “high C_(A) distilled aromatic extract feedstock” when usedwith respect to a feedstock, process stream, or product refers to aliquid material having a viscosity-gravity constant (VGC) close to 1(e.g., greater than about 0.95) as determined by ASTM D2501. Aromaticfeedstocks or process streams typically will contain at least about 10%C_(A) content and less than about 90% total C_(P) plus C_(N) content asmeasured according to ASTM D2140 or D3238, with the latter methodtypically being used for heavier petroleum fractions.

The term “ASTM” refers to the American Society for Testing and Materialswhich develops and publishes international and voluntary consensusstandards. Exemplary ASTM test methods are set out below. However,persons having ordinary skill in the art will recognize that standardsfrom other internationally recognized organizations will also beacceptable and may be used in place of or in addition to ASTM standards.

The term “enhanced C_(A) content napthenic process oil” refers to an oilhaving a greater C_(A) content than that of a comparison oil made bysimilarly hydrotreating at least one naphthenic vacuum gas oil alonewithout using the method of this disclosure.

The term “hydrocracking” refers to a process in which a feedstock orprocess stream is reacted with hydrogen in the presence of a catalyst atvery high temperatures and pressures, so as to crack and saturate themajority of the aromatic hydrocarbons present and eliminate all ornearly all sulfur-, nitrogen- and oxygen-containing compounds.

The term “hydrofinishing” refers to a process in which a feedstock orprocess stream is reacted with hydrogen in the presence of a catalystunder less severe conditions than for hydrotreating or hydrocracking, soas to saturate olefins and to some extent aromatic rings, and thusreduce the levels of PAH compounds and stabilize (e.g., reduce thelevels of) otherwise unstable molecules. Hydrofinishing may for examplebe used following hydrocracking to improve the color stability andstability towards oxidation of a hydrocracked product.

The term “hydrogenated” when used with respect to a feedstock, processstream or product refers to a material that has been hydrofinished,hydrotreated, reacted with hydrogen in the presence of a catalyst orotherwise subjected to a treatment process that materially increases thebound hydrogen content of the feedstock, process stream or product.

The term “hydrotreating” refers to a process in which a feedstock orprocess stream is reacted with hydrogen in the presence of a catalystunder more severe conditions than for hydrofinishing and under lesssevere conditions than for hydrocracking, so as to reduce unsaturation(e.g., aromatics) and reduce the amounts of sulfur-, nitrogen- oroxygen-containing compounds.

The term “liquid yield” when used with respect to a process stream orproduct refers to the weight percent of liquid products collected basedon the starting liquid material amount.

The term “naphthenic” when used with respect to a feedstock, processstream or product refers to a liquid material having a VGC from about0.85 to about 0.95 as determined by ASTM D2501. Naphthenic feedstockstypically will contain at least about 30% C_(N) content and less thanabout 70% total C_(P) plus C_(A) content as measured according to ASTMD2140.

The term “naphthenic blend stock” refers to a naphthenic crude residualbottom, naphthenic crude, naphthenic vacuum gas oil or naphthenicatmospheric gas oil for use in the disclosed method, viz., for use inblending with a disclosed feedstock.

The term “paraffinic” when used with respect to a feedstock, processstream or product refers to a liquid material having a VGC near 0.8(e.g., less than 0.85) as determined by ASTM D2501. Paraffinicfeedstocks typically will contain at least about 60 wt. % Cr content andless than about 40 wt. % total C_(N)+C_(A) content as measured accordingto ASTM D2140.

The terms “Viscosity-Gravity Constant” or “VGC” refer to an index forthe approximate characterization of the viscous fractions of petroleum.VGC formerly was defined as the general relation between specificgravity and Saybolt Universal viscosity. VGC may be determined based ondensity and viscosity measurements according to ASTM D2501. VGC isrelatively insensitive to molecular weight.

The term “viscosity” when used with respect to a feedstock, processstream or product refers to the kinematic viscosity of a liquid.Kinematic viscosities typically are expressed in units of mm²/s orcentistokes (cSt), and may be determined according to ASTM D445.Historically the petroleum industry has measured kinematic viscositiesin units of Saybolt Universal Seconds (SUS). Viscosities at differenttemperatures may be calculated according to ASTM D341 and converted fromcSt to SUS according to ASTM D2161.

Several embodiments of the disclosed method are schematicallyillustrated in FIG. 1 through FIG. 5 . Referring to FIG. 1 , a methodfor modifying naphthenic crude residual bottoms to provide a modifiednaphthenic process oil is shown. Steps 100 include vacuum distillingnaphthenic crude residual bottoms 110 in vacuum distillation unit 112 toprovide a naphthenic blend stock in the form of one or more vacuum gasoils 116, 118, 120 and 122 with respective nominal viscosities ofapproximately 60, 100, 500 and 2000 SUS at 38° C. (100° F.). A supply ofDAE feedstock from source unit 130 may be subjected to an optionalfractionation step 131 to isolate from the DAE feedstock a fraction thatdistills in the same general ranges as oil or oils present in thenaphthenic blend stock. Source unit 130 may for example be a solventextraction unit. DAE feedstock 132 from source unit 130 or fractionatingor extraction step 131 is provided to a blending unit (not shown in FIG.1 ) where at least vacuum gas oil 122 and DAE feedstock 132 are blendedtogether. In a typical distillation situation, vacuum gas oil 122 may bethe highest viscosity vacuum gas oil obtained from vacuum distillationunit 112. DAE feedstock 132 may if desired also or instead be blendedwith some or all of the remaining lower viscosity vacuum gas oilsobtained from unit 112, e.g., with one or more of the 60, 100 or 500 SUSvacuum gas oils 116, 118 or 120. Blending can be carried out using avariety of devices and procedures including mixing valves, staticmixers, mixing tanks and other techniques that will be familiar topersons having skill in the art.

Hydrotreatment unit 140 is employed to hydrotreat at least theabove-mentioned blend of vacuum gas oil 122 and DAE feedstock 132, anddesirably also to hydrotreat some or all of the remaining lowerviscosity vacuum gas oils obtained from unit 112, or to hydrotreatblends of such lower viscosity vacuum gas oils with DAE feedstock 132.The resulting naphthenic process oils 146, 148, 150 and 152 haverespective nominal

viscosities of approximately 60, 100, 500 and 2000 SUS at 38° C. (100°F.), and if hydrotreated also have reduced unsaturation and reducedamounts of sulfur-, nitrogen- or oxygen-containing compounds. Theresulting modified oils (for example, 500 SUS or 2000 SUS viscositynaphthenic process oil 152) may be used as a replacement for DAE processoils.

Referring to FIG. 2 , a method for modifying naphthenic crude to providea modified naphthenic process oil is shown. DAE feedstock source unit130, optional fractionation step 131, DAE feedstock 132 andhydrotreatment unit 140 are as described in FIG. 1 . Steps 200 includeatmospherically distilling naphthenic crude 206 in atmosphericdistillation unit 208 to provide atmospheric gas oils 214 and 216 withrespective nominal viscosities of approximately 40 and 60 SUS at 38° C.(100° F.) and atmospheric residue residual bottoms 210. Residual bottoms210 are vacuum distilled in vacuum distillation unit 112 to providevacuum gas oils 118, 120 and 122 with respective nominal viscosities ofapproximately 100, 500 and 2000 SUS at 38° C. (100° F.). Throughadjustment of the conditions in vacuum distillation unit 112, lowerviscosity vacuum gas oils, e.g., oils with a viscosity of approximately60 SUS at 38° C. (100° F.), may be obtained from unit 112 if desired.DAE feedstock 132 is provided to a blending unit (not shown in FIG. 2 )where at least vacuum gas oil 122 and DAE feedstock 132 are blendedtogether. DAE feedstock 132 may if desired also or instead be blendedwith some or all of the remaining lower viscosity vacuum gas oilsobtained from unit 112, e.g., with either or both the 100 or 500 SUSvacuum gas oils 118 or 120. Unit 140 is employed to hydrotreat at leastthe above-mentioned blend of vacuum gas oil 122 and DAE feedstock 132,any additional blends containing a lower viscosity vacuum gas oil andC_(A) feedstock 132, and desirably also some or all of the remaininglower viscosity vacuum gas oils obtained from unit 112 or theatmospheric gas oils obtained from unit 208. The resulting naphthenicprocess oils 244, 246, 148, 150 and 152 have respective nominalviscosities of approximately 40, 60, 100, 500 and 2000 SUS at 38° C.(100° F.), and if hydrotreated also have reduced unsaturation andreduced amounts of sulfur-, nitrogen- or oxygen-containing compounds.Modified oils such as 500 SUS or 2000 SUS viscosity naphthenic processoil 152 may be used as a replacement for DAE process oils.

Referring to FIG. 3 , another method for modifying naphthenic cruderesidual bottoms to provide a modified naphthenic process oil is shown.FIG. 3 is like FIG. 1 , but residual bottoms 110 are blended withfeedstock 132 and the blend subjected to vacuum distillation, ratherthan waiting until after the vacuum distillation step to carry outfeedstock blending. DAE feedstock source unit 130, optionalfractionation or extraction step 131, DAE feedstock 132 andhydrotreatment unit 140 are as described in FIG. 1 . Steps 300 includeblending naphthenic crude residual bottoms 110 with DAE feedstock 132obtained from DAE feedstock source unit 130 or from fractionating step131. Blending can be performed using a blending unit (not shown in FIG.3 ) and procedures that will be familiar to persons having skill in theart. The blend is then vacuum distilled in vacuum distillation unit 112to provide vacuum gas oils 316, 318, 320 and 322 with respective nominalviscosities of approximately 60, 100, 500 and 2000 SUS at 38° C. (100°F.). Unit 140 is employed to hydrotreat at least vacuum gas oil 322, anddesirably also to hydrotreat some or all of the remaining lowerviscosity vacuum gas oils obtained from unit 112, or to hydrotreatblends of such lower viscosity vacuum gas oils with DAE feedstock 132.The resulting naphthenic process oils 346, 348, 350 and 352 haverespective nominal viscosities of approximately 60, 100, 500 and 2000SUS at 38° C. (100° F.). When using the method shown in FIG. 3 , the DAEfeedstock can potentially affect the characteristics of all of thenaphthenic process oils made using the method, rather than merelyaffecting those with which the feedstock has been blended. Adistillation curve for the DAE feedstock when distilled by itself can beused to estimate the extent to which the feedstock will influence thecharacteristics of lower viscosity oils, with low boiling feedstockshaving a greater tendency to influence the characteristics of lowviscosity oils than will be the case for high boiling feedstocks. Thehydrotreated oils obtained from unit 140 will have reduced unsaturationand reduced amounts of sulfur-, nitrogen- or oxygen-containingcompounds. Modified oils such as 500 SUS or 2000 SUS viscositynaphthenic process oil 352 may be used as a replacement for DAE processoils.

Referring to FIG. 4 , another method for modifying naphthenic crude toprovide a modified naphthenic process oil is shown. FIG. 4 is like FIG.2 , but naphthenic crude 206 is blended with DAE feedstock 132 and theblend subjected to atmospheric and vacuum distillation, rather thanwaiting until later to carry out feedstock blending. DAE feedstocksource unit 130, optional fractionation step 131, DAE feedstock 132,hydrotreatment unit 140 and atmospheric distillation unit 208 are asdescribed in FIG. 2 . Steps 400 include blending naphthenic crude 206with DAE feedstock 132 obtained from DAE feedstock source unit 130 orfrom fractionating step 131. Blending can be performed using a blendingunit (not shown in FIG. 4 ) and procedures that will be familiar topersons having skill in the art. The blend is then atmosphericallydistilled in atmospheric distillation unit 208 to provide atmosphericgas oils 414 and 416 with respective nominal viscosities ofapproximately 40 and 60 SUS at 38° C. (100° F.) and atmospheric residueresidual bottoms 210. Residual bottoms 210 are vacuum distilled invacuum distillation unit 112 to provide vacuum gas oils 418, 420 and 422with respective nominal viscosities of approximately 100, 500 and 2000SUS at 38° C. (100° F.). Unit 140 is employed to hydrotreat at leastvacuum gas oil 422, and desirably also to hydrotreat some or all of theremaining lower viscosity vacuum gas oils or blends obtained from unit112 or some or all of the atmospheric gas oils obtained from unit 208.The resulting naphthenic process oils 444, 446, 448, 450 and 452 haverespective nominal viscosities of approximately 40, 60, 100, 500 and2000 SUS at 38° C. (100° F.), and if hydrotreated also have reducedunsaturation and reduced amounts of sulfur-, nitrogen- oroxygen-containing compounds. Modified oils such as 500 SUS or 2000 SUSviscosity naphthenic process oil 452 may be used as a replacement forDAE process oils.

Referring to FIG. 5 , another method for making a modified naphthenicprocess oil is shown. DAE feedstock source unit 130, optionalfractionation step 131, DAE feedstock 132 and hydrotreatment unit 140are as described in FIG. 1 . Steps 500 include blending naphthenicvacuum gas oil 522 with DAE feedstock 132 obtained from DAE feedstocksource unit 130 or from fractionating step 131. Vacuum gas oil 522 has aminimum viscosity of at least 60 SUS and preferably 500 SUS or 2000 SUSat 38° C. (100° F.). Blending can be performed using a blending unit(not shown in FIG. 5 ) and procedures that will be familiar to personshaving skill in the art. The blend is then hydrotreated in unit 140 toprovide naphthenic process oil 552 which may be used as a replacementfor DAE process oils.

Additional processing steps may optionally be employed before or afterthe steps mentioned above. Exemplary such steps include solventextraction, catalytic dewaxing, solvent dewaxing, hydrofinishing andhydrocracking. In some embodiments no additional processing steps areemployed, and in other embodiments additional processing steps such asany or all of deasphalting, solvent extraction, catalytic dewaxing,solvent dewaxing, hydrofinishing and hydrocracking are not required orare not employed.

A variety of naphthenic crude residual bottoms and naphthenic crudes maybe employed as naphthenic blend stocks in the disclosed method. Whennaphthenic crude residual bottoms are employed, they typically will beobtained from an atmospheric distillation unit for naphthenic crudesoperated in accordance with procedures that will be familiar to personshaving ordinary skill in the art, and normally will have a boiling pointabove about 370 to 380° C. When naphthenic crudes are employed in thedisclosed method, they may be obtained from a variety of sources.Exemplary naphthenic crudes include Brazilian, North Sea, West African,Australian, Canadian and Venezuelan naphthenic crudes from petroleumsuppliers including BHP Billiton Ltd., BP p.l.c., Chevron Corp.,ExxonMobil Corp., Mitsui & Co., Ltd., Royal Dutch Shell p.l.c.,Petrobras, Total S.A., Woodside Petroleum Ltd. and other suppliers thatwill be familiar to persons having ordinary skill in the art. The chosennaphthenic crude may for example have a VGC of at least about 0.85,0.855, 0.86 or 0.865, and a VGC less than about 1, 0.95. 0.9 or 0.895,as determined by ASTM D2501. Preferred naphthenic crudes will provide avacuum gas oil having a VGC from about 0.855 to 0.895. The chosen crudemay also contain at least about 30%, at least about 35% or at leastabout 40% C_(N) content, and less than about 70%, less than about 65% orless than about 60 total C_(P) plus C_(A) content as measured accordingto ASTM D2140.

A variety of naphthenic vacuum gas oils may be used as naphthenic blendstocks in the disclosed method. The vacuum gas oil may be used in anon-hydrotreated form, blended with the chosen feedstock, and then theresulting blended liquid may be hydrotreated. Alternatively, ahydrotreated naphthenic vacuum gas oil may be employed as the naphthenicblend stock, blended with the chosen feedstock, and then the resultingblended liquid may be further hydrotreated. Before it is hydrotreated,the chosen naphthenic vacuum gas oil may for example contain at leastabout 10%, at least about 12%, at least about 14%, at least about 16 orat least about 18% C_(A) content, and may also or instead contain lessthan about 24%, less than about 22%, less than about 21% or less thanabout 20% C_(A) content. Before hydrotreating, the chosen naphthenicvacuum gas oil may for example also or instead contain at least about40% or at least about 45% C_(A) plus C_(N) content.

Preferred hydrotreated naphthenic 60 SUS vacuum gas oils may for examplehave the following desirable characteristics separately or incombination: an aniline point (ASTM D611) of about 64° C. to about 85°C. or about 72° C. to about 77° C.; a flash point (Cleveland Open Cup,ASTM D92) of at least about 80° C. to about 230° C., or of at leastabout 136° C. to about 176° C.; a viscosity (SUS at 37.8° C.) of about35 to about 85 or about 54 to about 72; a pour point (° C., ASTM D5949)of about −90° C. to about −20° C. or about −75° C. to about −35° C.; andyields that are greater than 85 vol. %, e.g., greater than about 90%,greater than about 97%, or about 97% to about 99% of total lube yieldbased on feedstock.

Preferred hydrotreated naphthenic 100 SUS vacuum gas oils may forexample have the following desirable characteristics separately or incombination: an aniline point (ASTM D611) of about 64° C. to about 85°C. or about 72° C. to about 77° C.; a flash point (Cleveland Open Cup,ASTM D92) of at least about 90° C. to about 260° C., or of at leastabout 154° C. to about 196° C.; a viscosity (SUS at 37.8° C.) of about85 to about 135 or about 102 to about 113; a pour point (° C., ASTMD5949) of about −90° C. to about −12° C. or about −70° C. to about −30°C.; and yields that are greater than 85 vol. %, e.g., greater than about90%, greater than about 97%, or about 97% to about 99% of total lubeyield based on feedstock.

Preferred hydrotreated naphthenic 500 SUS vacuum gas oils may forexample have the following desirable characteristics separately or incombination: an aniline point (ASTM D611) of about 77° C. to about 98°C. or about 82° C. to about 92° C.; a flash point (Cleveland Open Cup,ASTM D92) of at least about 111° C. to about 333° C., or of at leastabout 167° C. to about 278° C.; a viscosity (SUS at 37.8° C.) of about450 to about 600 or about 500 to about 550; a pour point (° C., ASTMD5949) of about −73° C. to about −17° C. or about −51° C. to about −6°C.; and yields that are greater than 85 vol. %, e.g., greater than about90%, greater than about 97%, or about 97% to about 99%, of total lubeyield based on feedstock.

Preferred hydrotreated naphthenic 2000 vacuum gas oils may for examplehave the following desirable characteristics separately or incombination: an aniline point (ASTM D611) of about 90° C. to about 110°C. or about 93° C. to about 103° C.; a flash point (Cleveland Open Cup,ASTM D92) of at least about 168° C. to about 363° C., or of at leastabout 217° C. to about 314° C.; a viscosity (SUS at 37.8° C.) of about1700 to about 2500 or about 1900 to about 2300; a pour point (° C., ASTMD5949) of about −53° C. to about 24° C. or about −33° C. to about 6° C.;and yields that are greater than 85 vol. %, e.g., greater than about90%, greater than about 97%, or about 97% to about 99%, of total lubeyield based on feedstock.

Other desirable characteristics for the disclosed hydrotreatednaphthenic vacuum gas oils may include compliance with environmentalstandards such as EU Directive 2005/69/EC, IP346 and Modified AMEStesting ASTM E1687, to evaluate whether the finished product may becarcinogenic. These tests correlate with the concentration of polycyclicaromatic hydrocarbons. Desirably, the disclosed hydrotreated naphthenicvacuum gas oils have less than about 8 ppm, more desirably less thanabout 2 ppm and most desirably less than about 1 ppm of the sum of the8-markers when evaluated according to European standard EN 16143:2013.The latter values represent especially noteworthy 8-markers scores, andrepresent up to an order of magnitude improvement beyond the EUregulatory requirement.

Exemplary commercially available naphthenic vacuum gas oils, some ofwhich may already have been hydrotreated, include HYDROCAL™, HYDROSOL™and HR TUFFLO™ oils from Calumet Specialty Products Partners, LP;CORSOL™ RPO, CORSOL 1200, CORSOL 2000 and CORSOL 2400 oils from CrossOil and Refining Co., Inc.; HYPRENE™ L2000 oil from Ergon, Inc; NYTEX™230, NYTEX 810, NYTEX 820, NYTEX 832, NYTEX 840, NYTEX 8150, NYFLEX™220, NYFLEX 223, NYFLEX 820 and NYFLEX 3100 oils from Nynas AB; andRAFFENE™ 1200L, RAFFENE 2000L, HYNAP™ 500, HYNAP 2000 and HYNAP 4000oils from San Joaquin Refining Co., Inc.

The above-mentioned HYPRENE L2000 oil is a severely hydrotreated baseoil having the following typical test values:

TABLE 1 HYPRENE L2000 Properties Test description Test Method Test ValueAPI Gravity ASTM D1250 21.8 Sp. gr. @ 15.6/15.6° C. ASTM D1298 0.9230(60/60° F.) Sulfur, wt % ASTM D4294 0.085 Aniline Pt., ° C. ASTM D611 98Flash point, COC, ° C. ASTM D92 266 UV Absorp. @ 260 nm ASTM D2008 5.8Refractive Index @ 20° C. ASTM D1218 1.5080 Viscosity, cSt @38° C. (100°F.) ASTM D445 383 Viscosity, cSt. @99° C. (210° F.) ASTM D445 20Viscosity, SUS@38° C. (100° F.) ASTM D445 2093 Viscosity, SUS@99° C.(210° F.) ASTM D445 101 Color, ASTM ASTM D6045 L2.5 Pour Point, ° C.ASTM D5949 −14 VGC ASTM D2501 0.850 Clay Gel, wt. %: ASTM D2007Asphaltenes <0.1 Saturates 57.2 Polars 2.8 Aromatics 40.0 CarbonAnalysis ASTM D2140 C_(A), % 13 C_(N), % 32 C_(P), % 55 Tg, ° C. ASTMD3418 −54 PCA Extract IP 356 <3

Another exemplary hydrotreated naphthenic vacuum gas oil for use in thedisclosed method is available as TUFFLO™ 2000 from Calumet SpecialtyProducts Partners, LP with the following typical test values:

TABLE 2 TUFFLO 2000 Properties Test description Test Method Test ValueDensity @ 15° C., kg/m³ ASTM D4052 925 Aniline Pt., ° C. ASTM D611 97Viscosity, SUS@38° C. ASTM D445 2092 Viscosity, SUS@99° C. ASTM D445 96VGC ASTM D2501 0.849 Clay Gel, wt. %: ASTM D2007 Asphaltenes 0 Saturates60 Polars 2 Aromatics 38 Carbon Analysis ASTM D2140 C_(A), % 13 C_(N), %37 C_(P), % 50 Tg, ° C. ASTM D3418 −54

The above-mentioned HYPRENE L2000 and TUFFLO 2000 oils may be used as isin process oil applications. However, the disclosed method may be usedto improve such oils further by for example increasing their C_(A)content and improving their solubility in rubber formulations.

The vacuum distillation unit (and if used, the atmospheric distillationunit) may be operated in accordance with standard industry practicesthat will be familiar to persons having ordinary skill in the art.Vacuum gas oils and atmospheric gas oils having desired viscosity rangescan be obtained from such distillation units. Exemplary viscosity rangesinclude oils having a viscosity from about 60 to about 3,500, about 500to about 3,000 or about 1,000 to about 2,500 SUS at 38° C., andproperties like or unlike (e.g., between) those listed above fornaphthenic 60 and naphthenic 2000 vacuum gas oils.

DAEs for use in the disclosed method typically will be obtained from asolvent extraction unit that extracts an aromatic fraction from a crudedistillate, typically a paraffinic crude distillate, and operated inaccordance with procedures that will be familiar to persons havingordinary skill in the art. Exemplary DAEs will be extracts produced froma Group I solvent extraction process, and may be produced by companiesincluding BP p.l.c., Chevron Corp., ExxonMobil Corp., HollyFrontierCorp., PBF Energy, Inc. and Royal Dutch Shell p.l.c. The chosen DAE mayfor example contain at least about 20%, at least about 25% or at leastabout 30% CA content, and may be as high as 65% or more C_(A) content.As a generalization, addition of the DAE feedstock may increase C_(A),reduce the aniline point, increase UV absorption and refractive index,increase the VGC value compared to the starting naphthenic blend stockor vacuum gas oil, and increase the solvency of the process oil inrubber compounds. Use of a DAE feedstock may also increase C_(N) whilereducing C_(P), due for example to conversion of C_(A) from thefeedstock to saturated naphthenes (C_(N)) during the hydrotreating step.Increasing the C_(N) content may also increase solvency of the processoil in rubber compounds, although to a lesser degree than may beobserved for increased C_(A) content.

The naphthenic blend stock and DAE feedstock may be mixed in anyconvenient fashion, for example by adding the DAE feedstock to thenaphthenic blend stock or vice-versa. The naphthenic blend stock and DAEfeedstock may be mixed in a variety of ratios. The chosen mixing ratiocan readily be selected by persons skilled in the art, and may depend inpart on the chosen materials and their viscosities, C_(A) contents andPAH 8-marker values. Preferably the resulting blended liquid willcontain at least about 2, at least about 5 or at least about 10 wt. %DAE feedstock based on the weight of the blended liquid. Also, theblended liquid preferably will contain up to about 40, up to about 20 orup to about 15 wt. % DAE feedstock based on the weight of the blendedliquid. Extenders and rubber additives that will be familiar to thoseskilled in the art may also be added to the blended liquid if desired.

The blended liquid is hydrotreated. The primary purpose of hydrotreatingis to remove sulfur, nitrogen and polar compounds and to saturate somearomatic compounds. The hydrotreating step thus produces a first stageeffluent or hydrotreated effluent having at least a portion of thearomatics present in the blended liquid saturated, and the concentrationof sulfur- or nitrogen-containing heteroatom compounds decreased. Thehydrotreating step may be carried out by contacting the blended liquidwith a hydrotreating catalyst in the presence of hydrogen under suitablehydrotreating conditions, using any suitable reactor configuration.Exemplary reactor configurations include a fixed catalyst bed, fluidizedcatalyst bed, moving bed, slurry bed, counter current, and transfer flowcatalyst bed.

The hydrotreating catalyst is used in the hydrotreating step to removesulfur and nitrogen and typically includes a hydrogenation metal on asuitable catalyst support. The hydrogenation metal may include at leastone metal selected from Group 6 and Groups 8-10 of the Periodic Table(based on the IUPAC Periodic Table format having Groups from 1 to 18).The metal will generally be present in the catalyst composition in theform of an oxide or sulfide. Exemplary metals include iron, cobalt,nickel, tungsten, molybdenum, chromium and platinum. Particularlydesirable metals are cobalt, nickel, molybdenum and tungsten. Thesupport may be a refractory metal oxide, for example, alumina, silica orsilica-alumina. Exemplary commercially available hydrotreating catalystsinclude LH-23, DN-200, DN-3330, and DN-3620/3621 from Criterion.Companies such as Albemarle, Axens, Haldor Topsoe, and Advanced RefiningTechnologies also market suitable catalysts.

The temperature in the hydrotreating step typically may be about 260° C.(500° F.) to about 399° C. (750° F.), about 287° C. (550° F.) to about385° C. (725° F.), or about 307° C. (585° F.) to about 351° C. (665°F.). Exemplary hydrogen pressures that may be used in the hydrotreatingstage typically may be about 5,515 kPa (800 psig) to about 27,579 kPa(4,000 psig), about 8,273 kPa (1,200 psig) to about 22,063 kPa (3,200psig), or about 11,721 kPa (1700 psig) to about 20,684 kPa (3,000 psig).The quantity of hydrogen used to contact the feedstock may typically beabout 17.8 to about 1,780 m³/m³ (about 100 to about 10,000 standardcubic feet per barrel (scf/B)) of the feedstock stream, about 53.4 toabout 890.5 m³/m³ (about 300 to about 5,000 scf/B) or about 89.1 toabout 623.4 m³/m³ (500 to about 3,500 scf/B). Exemplary reaction timesbetween the hydrotreating catalyst and the feedstock may be chosen so asto provide a liquid hourly space velocity (LHSV) of about 0.25 to about5 cc of oil per cc of catalyst per hour (hr⁻¹), about 0.35 to about 1.5hr⁻¹, or about 0.5 to about 0.75 hr⁻¹.

The resulting modified naphthenic process oil may for example have thefollowing desirable characteristics separately or in combination: aflash point (Cleveland Open Cup, ASTM D92) of at least about 240° C.; aboiling point (corrected to atmospheric pressure) of about 320° to about650° C. or about 350° to about 600° C.; a kinematic viscosity of about15 to about 30 or about 18 to about 25 cSt @ 100° C.; a viscosity indexof about 5 to about 30; a pour point (ASTM D5949) of about −6° to about4° C.; an aromatic content (Clay Gel Analysis ASTM D2007) of about 30 toabout 55 weight percent, about 30 to about 50 weight percent or about 35to about 48 weight percent; a saturates content (Clay Gel Analysis ASTMD2007) of about 40 to about 65, about 40 to about 55 or about 42 toabout 52 weight percent; a polar compounds content (Clay Gel AnalysisASTM D2007) of about 0.4 to about 1, about 0.4 to about 0.9 or about 0.5to about 0.8 weight percent; a VGC of about 0.86 to about 0.89; a PCAextract content less than 3 weight percent, e.g. from 1 to 3 or 1 to 2weight percent, based on the total weight of hydrocarbons contained inthe oil composition as determined according to IP 346; and a PAH8-markers content less than 10 ppm when evaluated according to Europeanstandard EN 16143:2013.

The modified naphthenic process oil may be used in a variety of rubberformulations. Exemplary rubber formulations typically will contain ahigh proportion of aromatic groups, and include styrene-butadiene rubber(SBR), butadiene rubber (BR), ethylene-propylene-diene monomer rubber(EPDM) and natural rubber. Rubber formulations containing the modifiednaphthenic process oil may contain vulcanizing agents (e.g., sulfurcompounds), fillers or extenders (e.g., carbon black and silica) andother ingredients that will be familiar to persons having ordinary skillin the art. The rubber formulations may be cured to form a variety ofrubber-containing articles that will be familiar to persons havingordinary skill in the art, including tires, belts, hoses, gaskets andseals. The effect of the modified process oil may be assessed using avariety of tests that will be familiar to persons having ordinary skillin the art. For example, rubber formulations used to make tires may beevaluated by measuring wet grip (tan delta at 0° c.), rolling resistance(tan delta at 60° c.), skid resistance, abrasion resistance, drytraction and processability.

The invention is further illustrated in the following non-limitingexamples, in which all parts and percentages are by weight unlessotherwise indicated.

Example 1

LS2000 non-hydrotreated naphthenic vacuum gas oil (from Ergon, Inc., andhaving the properties shown below in Table 3) was combined at an 85:15volume ratio with ValAro™ 130A DAE (from Valero Marketing and SupplyCo., and having the properties shown below in Table 4) to form a blendedfeedstock identified as “DAE Blend”. In a series of runs identified asA-2, B-2, C-2 and D-2, the DAE Blend was subjected to a variety ofhydrotreating conditions. The conditions and properties of thenon-hydrotreated DAE Blend feedstock and the hydrotreated DAE Blends areshown below in Table 5:

TABLE 3 LS2000 Properties Test description Test Method Test Value APIGravity ASTM D1250 18.5 Sp. gr. @ 15.6/15.6° C. ASTM D1298 0.9437(60/60° F.) Sulfur, wt % ASTM D4294 0.6738 Aniline Pt., ° C. ASTM D61187 Flash point, COC, ° C. ASTM D92 282 UV Absorp. @ 260 nm ASTM D200815.6 Refractive Index @ 20° C. ASTM D1218 1.5240 Viscosity, cSt @38° C.(100° F.) ASTM D445 646 Viscosity, cSt. @99° C. (210° F.) ASTM D445 25Viscosity, SUS@38° C. (100° F.) ASTM D445 3595 Viscosity, SUS@99° C.(210° F) ASTM D445 126 Color, ASTM ASTM D6045 6.6 Pour Point, ° C. ASTMD5949 −12 VGC ASTM D2501 0.873 Clay Gel, wt. %: ASTM D2007 Asphaltenes<0.1 Saturates 46.2 Polars 10.4 Aromatics 43.4 Carbon Analysis ASTMD2140 C_(A), % 21 C_(N), % 33 C_(P), % 46 Distillation D2887 ASTM D2887Initial BP, ° C. (° F.) 376 (709)  5%, ° C. (° F.) 434 (814) 10%, ° C.(° F.) 450 (842) 30%, ° C. (° F.) 483 (901) 50%, ° C. (° F.) 506 (942)70%, ° C. (° F.) 529 (984) 90%, ° C. (° F.) 558 (1037) 95%, ° C. (° F.)570 (1058) Final BP, ° C. (° F.) 586 (1087)

TABLE 4 ValAro 130A Properties Test description Test Method Test ValueAPI Gravity ASTM D1250 9.7 Sp. gr. @ 15.6/15.6° C. (60/60° F.) ASTMD1298 0.990/1.017 Sulfur, wt % ASTM D4294 5.5 max Aniline Pt., ° C. ASTMD611 51.7 max Flash point, COC, ° C. ASTM D92 210 min Refractive Index @20° C. ASTM D1218, 1.5519 by extrapolation from diluted samplesViscosity, cSt. @100° C. (212° F.) ASTM D445 24/30 Viscosity, SUS@99° C.(210° F.) ASTM D445 118/149 Viscosity, SUS@38° C. (100° F.) ASTM D4457483 Viscosity, SUS@99° C. (210° F.) ASTM D445 143 Pour Point, ° C. ASTMD5949 30 max VGC ASTM D2501 0.925-0.965 Clay Gel, wt. %: ASTM D2007Asphaltenes 0.1 max Saturates Polars  7-16 Aromatics 65 min CarbonAnalysis ASTM D2140 C_(A), % 34 C_(N), % 54 C_(P), % 13 Carbon AnalysisASTM D3238 C_(A), % 31 C_(N), % 53 C_(P), % 16

TABLE 5 DAE Blend Feedstock and Hydrotreated DAE Blend PropertiesDescription Feedstock A-2 B-2 C-2 D-2 LHSV (hr⁻¹) — 0.56 0.67 0.62 0.63WRAT ° C. (° F.) — 329 (625) 329 (625) 343 (650) 315 (598) API Gravity13.04 20.7 20.56 21.16 20.12 Sp. gr. @ 15.6/15.6° C. 0.979 0.9297 0.93060.9269 0.9333 (60/60° F.) Sulfur, wt. % 3.808 0.31 0.316 0.206 0.41Sulfur, ppm 38081 3103 3162 2061 4095 Aniline Pt. ° C. (° F.)  61 (141) 93 (199)  92 (197)  93 (200)  91 (196) Flash point, COC, ° C. (° F.)257 (495) 252 (485) 260 (500) 260 (500) 263 (505) UV Absorp. @ 260 nm20.4 7.8 7.8 3.3 10.9 RI @ 20° C. out of 1.5131 1.5138 1.5109 1.5161range cSt @38° C. (100° F.) 960 432.2 464.3 421.6 515 cSt. @99° C. (210°F.) 127.5 19.5 20.2 19.2 21.2 SUS@38° C. (100° F.) 4449 2002 2151 19532384 SUS@99° C. (210° F.) 127.46 95.8 98.5 94.6 102.7 Color, ASTM TooDark 1.7 1.8 1.7 2 Pour Point, ° C. (° F.) 19 (66) −15 (5)  −15 (5)  −12(10)  −12 (10)  VGC 0.924 0.858 0.859 0.854 0.861 Nitrogen (total) ppmw1973 1009 1125 811 1330 NMR Wax, wt. % 5.85 3.12 3.01 3.23 1.75 NMRHydrogen Content, wt. % 9.035 11.087 10.917 11.188 10.636 HPLC Analysis,wt. %, D6591: Mono 17.26 29.30 28.34 29.80 26.18 Di 15.26 10.60 10.8411.46 10.16 Tri+ 44.34 18.38 19.31 15.98 20.65 Clay Gel, wt. %:Asphaltenes — — — — — Saturates 35.74 56.84 55.36 58.66 55.75 Polars0.64 0.43 0.45 0.41 0.44 Aromatics 63.62 42.73 44.19 40.93 43.81 CarbonAnalysis C_(A), % — 17 17 15 18 C_(N), % — 31 30 32 29 C_(P), % — 53 5353 52 Distillation D2887 Initial BP, ° C. 356 (673) 337 (638) 357 (674)347 (657) 375 (707) (° F.) 5%, ° C. 407 (764) 403 (758) 409 (768) 403(758) 414 (777) (° F.) 10%, ° C. 431 (808) 424 (796) 427 (801) 424 (795)431 (807) (° F.) 20%, ° C. 397 (747) 446 (835) 448 (838) 446 (834) 451(843) (° F.) 30%, ° C. 476 (888) 463 (865) 464 (867) 462 (863) 466 (871)(° F.) 40%, ° C. 488 (911) 477 (891) 478 (893) 476 (889) 480 (896) (°F.) 50%, ° C. 500 (932) 492 (917) 493 (919) 491 (916) 494 (922) (° F.)60%, ° C. 511 (951) 506 (942) 507 (944) 505 (941) 508 (946) (° F.) 70%,° C. 523 (973) 522 (971) 522 (972) 520 (968) 523 (974) (° F.) 80%, ° C.537 (998)  539 (1003)  539 (1003) 537 (999)  540 (1004) (° F.) 90%, ° C.(° F.)  556 (1033)  563 (1046)  562 (1043)  559 (1039)  562 (1044) 95%,° C. (° F.)  570 (1058)  577 (1071)  577 (1070)  574 (1066)  577 (1070)End Point, ° C. (° F.)  596 (1104)  607 (1124)  603 (1118)  599 (1110) 602 (1115) 8-markers by GC/MS 337.4 <1.0 <1.0 <1.0 33.2

The results shown in Table 5 demonstrate significant reductions in PAHlevels (as measured by 8-marker levels) and significant improvements inother finished product properties such as aniline point, refractiveindex, VGC and aromatic content. The C_(A) contents of the hydrotreatedblends were greater than the 13% C_(A) content of LS2000 naphthenicvacuum gas oil when similarly hydrotreated.

Example 2

The hydrotreated DAE Blends from Table 5 may be evaluated as processoils in a silica-filled passenger tire tread formulation containing theingredients shown below in Table 6. This tire tread formulation is notthat of any particular manufacturer, but instead represents acommonly-used formulation that is often employed in technical papers andother evaluations describing potential new rubber formulationingredients.

TABLE 6 Passenger tire tread compound formulation Loading, IngredientPHR Included in stage(s) Buna VSL Vp PBR 4041 unextended SBR 70Masterbatch, 1^(st) components rubber (Lanxess) Neo-cis BR rubber 30Masterbatch, 1^(st) components Process oil 37.5 Masterbatch, 1^(st),2^(nd) and 3^(rd) additions ZEOSIL ™ 1165MP silica filler (Rhodia) 80Masterbatch, 1^(st), 2^(nd) and 3^(rd) additions Wax 2.50 Masterbatch,3^(rd) addition SANTOFLEX ™ 6PPD antioxidant 1.00 Masterbatch, 3^(rd)addition (Eastman) poly(2,2,4-trimethyl-1,2- 1.00 Masterbatch, 3^(rd)addition dihydroquinoline) antioxidant (Flectol H) X50S ™ (1:1 blend ofSi 69 ™ and N330 12.8 Masterbatch, 2^(nd) addition carbon black, Evonik)Zinc oxide 3.00 Remill stage Stearic acid 2.00 Remill stage Sulfur 1.40Final stage Diphenylguanidine accelerator 2.00 Final stageN-t-butylbenzothiazole-2-sulfenamide 1.70 Final stage accelerator

The formulation ingredients may be mixed in a Banbury mixer at a batchweight of 3.3 kg using the mixing conditions shown below in Table 7. Therotor speed may be adjusted during the Masterbatch stage to prevent theMasterbatch temperature exceeding 155° C. In order to facilitate silanecoupling, the batch temperature may be held above 140° C. for 3 minutesfollowing addition of the X50S additive. A 3 minute remill stage may beemployed during which the rotor speed may be adjusted to keep thetemperature below 155° C. A 2 minute finalization stage may be employedduring which the rotor speed may be adjusted to keep the temperaturebelow 100° C.

TABLE 7 Mixing conditions Rotor speed, Coolant temperature, Stage rpm °C. Masterbatch 75 40 Remill 75 40 Finalize 50 40

Mooney viscosity characteristics of the resulting rubber formulationsmay be made at 100° C. using a Mooney rotating disc viscometer equippedwith a large rotor, and rheometric measurements may be made at 172° C.using a moving die rheometer and a 30 minute plot. Other physicalproperties that may be measured include dynamic properties at 10 Hz and1% strain over the temperature range −40 to 60° C., tensile strength inMPa, % extension at break, Shore A hardness, crescent tear strength,abrasion resistance index (Akron abrasion), compression set (7 days, 70°C.), Goodrich heat build-up characteristics, and loss angle (or tangentof the loss angle Tan δ) at about 60° and 0° respectively. Tan δ is ameasure of rubber hysteresis, viz., energy stored in the rubber that isnot recoverable as the rubber is stretched or compressed. For tireformulations normally a low Tan δ at 60° C. is indicative of a low tiretread rolling resistance, and a high Tan δ at 0° C. is indicative ofgood tread grip in wet conditions. Skid resistance may be measured usinga British Pendulum Skid Resistance apparatus operated according to BS EN13036-4 (2011) on smooth concrete block wet with room temperature (22°C.) distilled water, and with the test pieces being prepared using3-micrometer lapping paper. Higher values represent better skidresistance. For tire manufacturing, some test results have greaterimportance than others. As a generalization, results for processability,abrasion resistance, tan δ at 60° C. and 0° C., and skid resistance maybe especially important. Tensile samples and hardness buttons made fromeach rubber formulation may also be aged in a laboratory fan convectionoven at 70° C. for 7 days and evaluated for changes in the abovephysical properties.

The above description is directed to the disclosed processes and is notintended to limit them. Those of skill in the art will readilyappreciate that the teachings found herein may be applied to yet otherembodiments within the scope of the attached claims. The completedisclosures of all cited patents, patent documents, and publications areincorporated herein by reference as if individually incorporated.However, in case of any inconsistencies the present disclosure,including any definitions herein, will prevail.

1. A method for making naphthenic process oils, the method comprising:a1) vacuum distilling residual bottoms from a naphthenic crudeatmospheric distillation unit to provide one or more vacuum gas oils inone or more viscosity ranges; or a2) atmospheric distilling naphtheniccrude to provide one or more atmospheric gas oils in one or moreviscosity ranges and residual bottoms, and vacuum distilling theresidual bottoms to provide one or more vacuum gas oils in one or moreviscosity ranges; b) blending at least one such vacuum gas oil with ahigh C_(A) distilled aromatic extract feedstock to provide at least oneblended oil; and c) hydrotreating the at least one blended oil toprovide an enhanced C_(A) content naphthenic process oil; wherein thehigh C_(A) distilled aromatic extract feedstock and enhanced C_(A)content naphthenic process oil each have greater C_(A) content than thatof a comparison oil made by similarly hydrotreating the one or morevacuum gas oils alone.
 2. The method according to claim 1 wherein vacuumdistilled residual bottoms from a naphthenic crude atmosphericdistillation unit provide the at least one such vacuum gas oil.
 3. Themethod according to claim 1 wherein atmospheric distilled naphtheniccrude provides the one or more atmospheric gas oils in one or moreviscosity ranges and residual bottoms, and wherein the residual bottomsare vacuum distilled to provide the at least one such vacuum gas oil. 4.The method according to claim 1 wherein the at least one such vacuum gasoil contains at least about 10% C_(A) content.
 5. The method accordingto claim 1 wherein the distilled aromatic extract feedstock isfractionated to isolate oils that distill in the same general range asat least one of the vacuum gas oils.
 6. The method according to claim 1wherein the blended oil contains about 2 to about 40 wt. % distilledaromatic extract feedstock based on the weight of the blended oil. 7.The method according to claim 1 wherein the at least one such vacuum gasoil has a viscosity from about 100 to about 3,500 SUS at 38° C.
 8. Themethod according to claim 1 wherein the enhanced C_(A) contentnaphthenic process oil has a viscosity of about 100 to about 2000 SUS at38° C.
 9. The method according to claim 1 wherein the enhanced C_(A)content naphthenic process oil has reduced unsaturation and reducedamounts of sulfur-, nitrogen- or oxygen-containing compounds compared tothe at least one such vacuum gas oil.
 10. The method according to claim1 wherein the enhanced C_(A) content naphthenic process oil hasincreased C_(A) content, reduced aniline point, increased UV absorptionand refractive index, and increased VGC value compared to the at leastone such vacuum gas oil.
 11. The method according to claim 1 wherein theenhanced C_(A) content naphthenic process oil has less than about 10 ppmPAH 8-markers when evaluated according to European standard EN16143:2013.
 12. The method according to claim 1 further comprising astep of solvent extraction, catalytic dewaxing, solvent dewaxing,hydrofinishing or hydrocracking.
 13. The method according to claim 1wherein steps of deasphalting, solvent extraction, catalytic dewaxing,solvent dewaxing, hydrofinishing and hydrocracking are not employed. 14.The method according to claim 1 wherein the enhanced C_(A) contentnaphthenic process oil has the following desirable characteristicsseparately or in combination: a flash point according to Cleveland OpenCup, ASTM D92 of at least about 240° C.; a boiling point (corrected toatmospheric pressure) of about 320° to about 650° C.; a kinematicviscosity of about 15 to about 30 cSt @ 100° C. according to ASTM D445;a viscosity index of about 5 to about 30; a pour point according to ASTMD5949 of about −6° to about 4° C.; an aromatic content according to ClayGel Analysis ASTM D2007 of about 30 to about 55 weight percent; asaturates content (Clay Gel Analysis ASTM D2007) of about 40 to about 65weight percent; a polar compounds content according to Clay Gel AnalysisASTM D2007 of about 0.4 to about 1 weight percent; a VGC of about 0.86to about 0.89; a PCA extract content less than 3 weight percent asdetermined according to IP 346; and a PAH 8-markers content less than 10ppm when evaluated according to European standard EN 16143:2013.
 15. Themethod according to claim 1 further comprising combining the enhancedC_(A) content naphthenic process oil with a rubber formulation.
 16. Amethod for making naphthenic process oils, the method comprising: a)blending a naphthenic vacuum gas oil having a viscosity of at least 60SUS at 38° C. with a high C_(A) distilled aromatic extract feedstock toprovide a blended oil; and b) hydrotreating the blended oil to providean enhanced C_(A) content naphthenic process oil; wherein the feedstockand enhanced C_(A) content naphthenic process oil each have greaterC_(A) content than that of a comparison oil made by similarlyhydrotreating the naphthenic vacuum gas oil alone.
 17. A naphthenicprocess oil comprising a hydrotreated blend of a) at least onenaphthenic vacuum gas oil having a viscosity of at least 60 SUS at 38°C. and b) a high C_(A) distilled aromatic extract feedstock havinggreater C_(A) content than that of a comparison oil made by similarlyhydrotreating the at least one naphthenic vacuum gas oil alone.